Primordial oocytes of C57Bl/6N(B6) mice are sensitive to polycyclic aromatic hydrocarbons (PAH). When B6 mice are treated with PAH nearly all of the primordial oocytes are destroyed within several days. The objective of this study is to determine how cell organelles of granulosa cells and oocytes are effected by the PAH treatment. Fine structural studies are in progress on ovaries of B6 mice obtained 2, 3 and 4 days after exposure to PAH.